/*
 * jidctred.c
 *
 * Copyright (C) 1994, Thomas G. Lane.
 * This file is part of the Independent JPEG Group's software.
 * For conditions of distribution and use, see the accompanying README file.
 *
 * This file contains inverse-DCT routines that produce reduced-size output:
 * either 4x4, 2x2, or 1x1 pixels from an 8x8 DCT block.
 *
 * The implementation is based on the Loeffler, Ligtenberg and Moschytz (LL&M)
 * algorithm used in jidctint.c.  We simply replace each 8-to-8 1-D IDCT step
 * with an 8-to-4 step that produces the four averages of two adjacent outputs
 * (or an 8-to-2 step producing two averages of four outputs, for 2x2 output).
 * These steps were derived by computing the corresponding values at the end
 * of the normal LL&M code, then simplifying as much as possible.
 *
 * 1x1 is trivial: just take the DC coefficient divided by 8.
 *
 * See jidctint.c for additional comments.
 */

#define JPEG_INTERNALS
#include "jinclude.h"
#include "jpeglib.h"
#include "jdct.h"        /* Private declarations for DCT subsystem */

#ifdef IDCT_SCALING_SUPPORTED


/*
 * This module is specialized to the case DCTSIZE = 8.
 */

#if DCTSIZE != 8
Sorry, this code only copes with 8 x8 DCTs.  /* deliberate syntax err */
    #endif


/* Scaling is the same as in jidctint.c. */

#if BITS_IN_JSAMPLE == 8
#define CONST_BITS  13
#define PASS1_BITS  2
#else
#define CONST_BITS  13
#define PASS1_BITS  1       /* lose a little precision to avoid overflow */
#endif

/* Some C compilers fail to reduce "FIX(constant)" at compile time, thus
 * causing a lot of useless floating-point operations at run time.
 * To get around this we use the following pre-calculated constants.
 * If you change CONST_BITS you may want to add appropriate values.
 * (With a reasonable C compiler, you can just rely on the FIX() macro...)
 */

#if CONST_BITS == 13
#define FIX_0_211164243  ( (INT32)  1730 )    /* FIX(0.211164243) */
#define FIX_0_509795579  ( (INT32)  4176 )    /* FIX(0.509795579) */
#define FIX_0_601344887  ( (INT32)  4926 )    /* FIX(0.601344887) */
#define FIX_0_720959822  ( (INT32)  5906 )    /* FIX(0.720959822) */
#define FIX_0_765366865  ( (INT32)  6270 )    /* FIX(0.765366865) */
#define FIX_0_850430095  ( (INT32)  6967 )    /* FIX(0.850430095) */
#define FIX_0_899976223  ( (INT32)  7373 )    /* FIX(0.899976223) */
#define FIX_1_061594337  ( (INT32)  8697 )    /* FIX(1.061594337) */
#define FIX_1_272758580  ( (INT32)  10426 )   /* FIX(1.272758580) */
#define FIX_1_451774981  ( (INT32)  11893 )   /* FIX(1.451774981) */
#define FIX_1_847759065  ( (INT32)  15137 )   /* FIX(1.847759065) */
#define FIX_2_172734803  ( (INT32)  17799 )   /* FIX(2.172734803) */
#define FIX_2_562915447  ( (INT32)  20995 )   /* FIX(2.562915447) */
#define FIX_3_624509785  ( (INT32)  29692 )   /* FIX(3.624509785) */
#else
#define FIX_0_211164243  FIX( 0.211164243 )
#define FIX_0_509795579  FIX( 0.509795579 )
#define FIX_0_601344887  FIX( 0.601344887 )
#define FIX_0_720959822  FIX( 0.720959822 )
#define FIX_0_765366865  FIX( 0.765366865 )
#define FIX_0_850430095  FIX( 0.850430095 )
#define FIX_0_899976223  FIX( 0.899976223 )
#define FIX_1_061594337  FIX( 1.061594337 )
#define FIX_1_272758580  FIX( 1.272758580 )
#define FIX_1_451774981  FIX( 1.451774981 )
#define FIX_1_847759065  FIX( 1.847759065 )
#define FIX_2_172734803  FIX( 2.172734803 )
#define FIX_2_562915447  FIX( 2.562915447 )
#define FIX_3_624509785  FIX( 3.624509785 )
#endif


/* Multiply an INT32 variable by an INT32 constant to yield an INT32 result.
 * For 8-bit samples with the recommended scaling, all the variable
 * and constant values involved are no more than 16 bits wide, so a
 * 16x16->32 bit multiply can be used instead of a full 32x32 multiply.
 * For 12-bit samples, a full 32-bit multiplication will be needed.
 */

#if BITS_IN_JSAMPLE == 8
#define MULTIPLY( var, const )  MULTIPLY16C16( var, const )
#else
#define MULTIPLY( var, const )  ( ( var ) * ( const ) )
#endif


/* Dequantize a coefficient by multiplying it by the multiplier-table
 * entry; produce an int result.  In this module, both inputs and result
 * are 16 bits or less, so either int or short multiply will work.
 */

#define DEQUANTIZE( coef, quantval )  ( ( (ISLOW_MULT_TYPE) ( coef ) ) * ( quantval ) )


/*
 * Perform dequantization and inverse DCT on one block of coefficients,
 * producing a reduced-size 4x4 output block.
 */

GLOBAL void
jpeg_idct_4x4( j_decompress_ptr cinfo, jpeg_component_info * compptr,
               JCOEFPTR coef_block,
               JSAMPARRAY output_buf, JDIMENSION output_col ) {
    INT32 tmp0, tmp2, tmp10, tmp12;
    INT32 z1, z2, z3, z4;
    JCOEFPTR inptr;
    ISLOW_MULT_TYPE * quantptr;
    int * wsptr;
    JSAMPROW outptr;
    JSAMPLE * range_limit = IDCT_range_limit( cinfo );
    int ctr;
    int workspace[DCTSIZE * 4];/* buffers data between passes */
    SHIFT_TEMPS

    /* Pass 1: process columns from input, store into work array. */

    inptr = coef_block;
    quantptr = (ISLOW_MULT_TYPE *) compptr->dct_table;
    wsptr = workspace;
    for ( ctr = DCTSIZE; ctr > 0; inptr++, quantptr++, wsptr++, ctr-- ) {
        /* Don't bother to process column 4, because second pass won't use it */
        if ( ctr == DCTSIZE - 4 ) {
            continue;
        }
        if ( ( inptr[DCTSIZE * 1] | inptr[DCTSIZE * 2] | inptr[DCTSIZE * 3] |
               inptr[DCTSIZE * 5] | inptr[DCTSIZE * 6] | inptr[DCTSIZE * 7] ) == 0 ) {
            /* AC terms all zero; we need not examine term 4 for 4x4 output */
            int dcval = DEQUANTIZE( inptr[DCTSIZE * 0], quantptr[DCTSIZE * 0] ) << PASS1_BITS;

            wsptr[DCTSIZE * 0] = dcval;
            wsptr[DCTSIZE * 1] = dcval;
            wsptr[DCTSIZE * 2] = dcval;
            wsptr[DCTSIZE * 3] = dcval;

            continue;
        }

        /* Even part */

        tmp0 = DEQUANTIZE( inptr[DCTSIZE * 0], quantptr[DCTSIZE * 0] );
        tmp0 <<= ( CONST_BITS + 1 );

        z2 = DEQUANTIZE( inptr[DCTSIZE * 2], quantptr[DCTSIZE * 2] );
        z3 = DEQUANTIZE( inptr[DCTSIZE * 6], quantptr[DCTSIZE * 6] );

        tmp2 = MULTIPLY( z2, FIX_1_847759065 ) + MULTIPLY( z3, -FIX_0_765366865 );

        tmp10 = tmp0 + tmp2;
        tmp12 = tmp0 - tmp2;

        /* Odd part */

        z1 = DEQUANTIZE( inptr[DCTSIZE * 7], quantptr[DCTSIZE * 7] );
        z2 = DEQUANTIZE( inptr[DCTSIZE * 5], quantptr[DCTSIZE * 5] );
        z3 = DEQUANTIZE( inptr[DCTSIZE * 3], quantptr[DCTSIZE * 3] );
        z4 = DEQUANTIZE( inptr[DCTSIZE * 1], quantptr[DCTSIZE * 1] );

        tmp0 = MULTIPLY( z1, -FIX_0_211164243 )/* sqrt(2) * (c3-c1) */
               + MULTIPLY( z2, FIX_1_451774981 )/* sqrt(2) * (c3+c7) */
               + MULTIPLY( z3, -FIX_2_172734803 )/* sqrt(2) * (-c1-c5) */
               + MULTIPLY( z4, FIX_1_061594337 );/* sqrt(2) * (c5+c7) */

        tmp2 = MULTIPLY( z1, -FIX_0_509795579 )/* sqrt(2) * (c7-c5) */
               + MULTIPLY( z2, -FIX_0_601344887 )/* sqrt(2) * (c5-c1) */
               + MULTIPLY( z3, FIX_0_899976223 )/* sqrt(2) * (c3-c7) */
               + MULTIPLY( z4, FIX_2_562915447 );/* sqrt(2) * (c1+c3) */

        /* Final output stage */

        wsptr[DCTSIZE * 0] = (int) DESCALE( tmp10 + tmp2, CONST_BITS - PASS1_BITS + 1 );
        wsptr[DCTSIZE * 3] = (int) DESCALE( tmp10 - tmp2, CONST_BITS - PASS1_BITS + 1 );
        wsptr[DCTSIZE * 1] = (int) DESCALE( tmp12 + tmp0, CONST_BITS - PASS1_BITS + 1 );
        wsptr[DCTSIZE * 2] = (int) DESCALE( tmp12 - tmp0, CONST_BITS - PASS1_BITS + 1 );
    }

    /* Pass 2: process 4 rows from work array, store into output array. */

    wsptr = workspace;
    for ( ctr = 0; ctr < 4; ctr++ ) {
        outptr = output_buf[ctr] + output_col;
        /* It's not clear whether a zero row test is worthwhile here ... */

#ifndef NO_ZERO_ROW_TEST
        if ( ( wsptr[1] | wsptr[2] | wsptr[3] | wsptr[5] | wsptr[6] |
               wsptr[7] ) == 0 ) {
            /* AC terms all zero */
            JSAMPLE dcval = range_limit[(int) DESCALE( (INT32) wsptr[0], PASS1_BITS + 3 )
                                        & RANGE_MASK];

            outptr[0] = dcval;
            outptr[1] = dcval;
            outptr[2] = dcval;
            outptr[3] = dcval;

            wsptr += DCTSIZE;/* advance pointer to next row */
            continue;
        }
#endif

        /* Even part */

        tmp0 = ( (INT32) wsptr[0] ) << ( CONST_BITS + 1 );

        tmp2 = MULTIPLY( (INT32) wsptr[2], FIX_1_847759065 )
               + MULTIPLY( (INT32) wsptr[6], -FIX_0_765366865 );

        tmp10 = tmp0 + tmp2;
        tmp12 = tmp0 - tmp2;

        /* Odd part */

        z1 = (INT32) wsptr[7];
        z2 = (INT32) wsptr[5];
        z3 = (INT32) wsptr[3];
        z4 = (INT32) wsptr[1];

        tmp0 = MULTIPLY( z1, -FIX_0_211164243 )/* sqrt(2) * (c3-c1) */
               + MULTIPLY( z2, FIX_1_451774981 )/* sqrt(2) * (c3+c7) */
               + MULTIPLY( z3, -FIX_2_172734803 )/* sqrt(2) * (-c1-c5) */
               + MULTIPLY( z4, FIX_1_061594337 );/* sqrt(2) * (c5+c7) */

        tmp2 = MULTIPLY( z1, -FIX_0_509795579 )/* sqrt(2) * (c7-c5) */
               + MULTIPLY( z2, -FIX_0_601344887 )/* sqrt(2) * (c5-c1) */
               + MULTIPLY( z3, FIX_0_899976223 )/* sqrt(2) * (c3-c7) */
               + MULTIPLY( z4, FIX_2_562915447 );/* sqrt(2) * (c1+c3) */

        /* Final output stage */

        outptr[0] = range_limit[(int) DESCALE( tmp10 + tmp2,
                                               CONST_BITS + PASS1_BITS + 3 + 1 )
                                & RANGE_MASK];
        outptr[3] = range_limit[(int) DESCALE( tmp10 - tmp2,
                                               CONST_BITS + PASS1_BITS + 3 + 1 )
                                & RANGE_MASK];
        outptr[1] = range_limit[(int) DESCALE( tmp12 + tmp0,
                                               CONST_BITS + PASS1_BITS + 3 + 1 )
                                & RANGE_MASK];
        outptr[2] = range_limit[(int) DESCALE( tmp12 - tmp0,
                                               CONST_BITS + PASS1_BITS + 3 + 1 )
                                & RANGE_MASK];

        wsptr += DCTSIZE;   /* advance pointer to next row */
    }
}


/*
 * Perform dequantization and inverse DCT on one block of coefficients,
 * producing a reduced-size 2x2 output block.
 */

GLOBAL void
jpeg_idct_2x2( j_decompress_ptr cinfo, jpeg_component_info * compptr,
               JCOEFPTR coef_block,
               JSAMPARRAY output_buf, JDIMENSION output_col ) {
    INT32 tmp0, tmp10, z1;
    JCOEFPTR inptr;
    ISLOW_MULT_TYPE * quantptr;
    int * wsptr;
    JSAMPROW outptr;
    JSAMPLE * range_limit = IDCT_range_limit( cinfo );
    int ctr;
    int workspace[DCTSIZE * 2];/* buffers data between passes */
    SHIFT_TEMPS

    /* Pass 1: process columns from input, store into work array. */

    inptr = coef_block;
    quantptr = (ISLOW_MULT_TYPE *) compptr->dct_table;
    wsptr = workspace;
    for ( ctr = DCTSIZE; ctr > 0; inptr++, quantptr++, wsptr++, ctr-- ) {
        /* Don't bother to process columns 2,4,6 */
        if ( ( ctr == DCTSIZE - 2 ) || ( ctr == DCTSIZE - 4 ) || ( ctr == DCTSIZE - 6 ) ) {
            continue;
        }
        if ( ( inptr[DCTSIZE * 1] | inptr[DCTSIZE * 3] |
               inptr[DCTSIZE * 5] | inptr[DCTSIZE * 7] ) == 0 ) {
            /* AC terms all zero; we need not examine terms 2,4,6 for 2x2 output */
            int dcval = DEQUANTIZE( inptr[DCTSIZE * 0], quantptr[DCTSIZE * 0] ) << PASS1_BITS;

            wsptr[DCTSIZE * 0] = dcval;
            wsptr[DCTSIZE * 1] = dcval;

            continue;
        }

        /* Even part */

        z1 = DEQUANTIZE( inptr[DCTSIZE * 0], quantptr[DCTSIZE * 0] );
        tmp10 = z1 << ( CONST_BITS + 2 );

        /* Odd part */

        z1 = DEQUANTIZE( inptr[DCTSIZE * 7], quantptr[DCTSIZE * 7] );
        tmp0 = MULTIPLY( z1, -FIX_0_720959822 );/* sqrt(2) * (c7-c5+c3-c1) */
        z1 = DEQUANTIZE( inptr[DCTSIZE * 5], quantptr[DCTSIZE * 5] );
        tmp0 += MULTIPLY( z1, FIX_0_850430095 );/* sqrt(2) * (-c1+c3+c5+c7) */
        z1 = DEQUANTIZE( inptr[DCTSIZE * 3], quantptr[DCTSIZE * 3] );
        tmp0 += MULTIPLY( z1, -FIX_1_272758580 );/* sqrt(2) * (-c1+c3-c5-c7) */
        z1 = DEQUANTIZE( inptr[DCTSIZE * 1], quantptr[DCTSIZE * 1] );
        tmp0 += MULTIPLY( z1, FIX_3_624509785 );/* sqrt(2) * (c1+c3+c5+c7) */

        /* Final output stage */

        wsptr[DCTSIZE * 0] = (int) DESCALE( tmp10 + tmp0, CONST_BITS - PASS1_BITS + 2 );
        wsptr[DCTSIZE * 1] = (int) DESCALE( tmp10 - tmp0, CONST_BITS - PASS1_BITS + 2 );
    }

    /* Pass 2: process 2 rows from work array, store into output array. */

    wsptr = workspace;
    for ( ctr = 0; ctr < 2; ctr++ ) {
        outptr = output_buf[ctr] + output_col;
        /* It's not clear whether a zero row test is worthwhile here ... */

#ifndef NO_ZERO_ROW_TEST
        if ( ( wsptr[1] | wsptr[3] | wsptr[5] | wsptr[7] ) == 0 ) {
            /* AC terms all zero */
            JSAMPLE dcval = range_limit[(int) DESCALE( (INT32) wsptr[0], PASS1_BITS + 3 )
                                        & RANGE_MASK];

            outptr[0] = dcval;
            outptr[1] = dcval;

            wsptr += DCTSIZE;/* advance pointer to next row */
            continue;
        }
#endif

        /* Even part */

        tmp10 = ( (INT32) wsptr[0] ) << ( CONST_BITS + 2 );

        /* Odd part */

        tmp0 = MULTIPLY( (INT32) wsptr[7], -FIX_0_720959822 )/* sqrt(2) * (c7-c5+c3-c1) */
               + MULTIPLY( (INT32) wsptr[5], FIX_0_850430095 )/* sqrt(2) * (-c1+c3+c5+c7) */
               + MULTIPLY( (INT32) wsptr[3], -FIX_1_272758580 )/* sqrt(2) * (-c1+c3-c5-c7) */
               + MULTIPLY( (INT32) wsptr[1], FIX_3_624509785 );/* sqrt(2) * (c1+c3+c5+c7) */

        /* Final output stage */

        outptr[0] = range_limit[(int) DESCALE( tmp10 + tmp0,
                                               CONST_BITS + PASS1_BITS + 3 + 2 )
                                & RANGE_MASK];
        outptr[1] = range_limit[(int) DESCALE( tmp10 - tmp0,
                                               CONST_BITS + PASS1_BITS + 3 + 2 )
                                & RANGE_MASK];

        wsptr += DCTSIZE;   /* advance pointer to next row */
    }
}


/*
 * Perform dequantization and inverse DCT on one block of coefficients,
 * producing a reduced-size 1x1 output block.
 */

GLOBAL void
jpeg_idct_1x1( j_decompress_ptr cinfo, jpeg_component_info * compptr,
               JCOEFPTR coef_block,
               JSAMPARRAY output_buf, JDIMENSION output_col ) {
    int dcval;
    ISLOW_MULT_TYPE * quantptr;
    JSAMPLE * range_limit = IDCT_range_limit( cinfo );
    SHIFT_TEMPS

    /* We hardly need an inverse DCT routine for this: just take the
     * average pixel value, which is one-eighth of the DC coefficient.
     */
    quantptr = (ISLOW_MULT_TYPE *) compptr->dct_table;
    dcval = DEQUANTIZE( coef_block[0], quantptr[0] );
    dcval = (int) DESCALE( (INT32) dcval, 3 );

    output_buf[0][output_col] = range_limit[dcval & RANGE_MASK];
}

#endif /* IDCT_SCALING_SUPPORTED */
